Do Cough Drops Expire?
Yes, cough drops do expire.
Producers print the expiration date on the package of the drop, not without reason. This date indicates how long the product is effective when stored properly [1]. That is why expired cough drops will often have little to no effect on the cough.
Why do Cough Drops Expire?
Cough drops are liquid mixtures of multiple substances. The composition depends on the manufacturers. However, regardless of the origin, chemical products change over time. Some of the ingredients can evaporate, others can change their form [1].
Over time, the alternations in the cough drop lead mostly to a decrease in effectiveness [1].
What Substances are Found in Cough Drops?
The primary and most important substance in cough drops is the active element. A commonly found active substance in cough drops is menthol [2].
Menthol is used in cough drops to relax the smooth muscles in the bronchial tree and also the deeper terminal bronchioles [3]. The relaxation increases the lumen of the airways, making it easier to cough out the mucus.
Additionally, menthol is a mild anesthetic. It relieves the irritation in the upper airways.
Also, other substances are found in cough drops. They are called excipients and are added to enhance stability and medication delivery [4].
What are the Factors Influencing the Durability of Cough Drops?
The durability of cough drops can be influenced by several factors, including:
- their composition,
- storage conditions,
- presence of certain additives.
A primary factor is the composition of the cough drops. For instance, cough drops can contain certain active ingredients like menthol, cineole, thymol, or (E)-anethole [5]. The biochemical form in which those active substances exist is key. The durability of the whole medication depends on these factors.
The storage conditions also play a crucial role in the durability of cough drops. Environmental factors like temperature, UV radiation, or pH affect the stability of the active substances [6].
Also, additives and excipients in the cough drops impact the durability of the formula. For example, the drops based on glycerol have better stability. This sugar alcohol increases the density of the cough drops [7]. The viscose composition makes the medication more stable.
How is the Expiration Date of Cough Drops Determined?
The expiration date of cough drops, like any other medicine, is determined through stress tests. During this evaluation, the drops are exposed to various different temperatures, light conditions, and humidity [1].
The tests show how the medication changes depending on the storage time and conditions. In every case, the absorption and the effect on the organism are also reviewed. All of this is done to ensure the highest safety and effectiveness of the cough drops and any other drug.
Can Expired Cough Drops be Harmful?
There is no clear evidence suggesting that expired cough drops can be harmful.
However, with time or inappropriate storage, cough drops lose their therapeutic effectiveness [1]. Therefore, drops that are expired or have been exposed to, for example, high temperatures should be substituted with new ones.